* New possibility to invoke user queries from a search expression
From the search field: `S:"My query"`.
Can be combined with other filters such as `S:"My query" date:P3d` as long as the user queries do not contain `OR`.
A use-case is to have an RSS filter with a stable address or an external API call with the ability to update the user query.
* Draft of parenthesis logic
* More draft
* Working parenthesis (a OR b) (c OR d)
* Working (A) OR (B)
* Support nested parentheses + unit tests + documentation
* search:MySearch and S:3
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